In oil and gas well operations, various methods have been developed for stimulating production of well bores associated with a reservoir. For example, wellbore fracturing technology has been suggested in order to increase permeability of reservoirs.
It has been suggested that well production can be improved by fracturing formations. Fracturing is typically done by pumping a formation full of a fracturing fluid and pressurizing that fluid in order to apply large surface forces to parts of the formation. These large surface forces cause stresses, and by virtue of the massive areas involved, can produce extremely high forces and stresses in the rock formations.
Accordingly, the rock formations tend to shatter, causing fractures in the reservoir rock, thereby increasing porosity and providing space for the produced fluids, such as oil and/or gas, to pass through the formation toward the bore hole for extraction.
Proppant is sometimes employed with the fracturing fluid to prop open the fractures when they form. Proppant is a granulated material each granule having a hard inner substrate such as of sand, resin, shell, ceramic, etc. The difficulty has been how to maintain the proppants suspended in the fluid in order to carry it downhole into the fracture.
Self-suspending proppant has been developed. Self-suspending proppant includes the hard proppant inner substrate coated with a water absorbing polymer coating. Such a proppant may be mixed with a liquid to form a fracturing fluid, and the coating reacts with the liquid to form fracturing fluid with a viscosity, resistance to settling and other features. A self-suspending proppant reduces the need for separately added viscosifiers. However, self-suspending proppant is more expensive than untreated proppant.